I've wondered about this too. I will say this though, about two weeks ago I had turned off my tablet the night before a class and it had "2 hours in-use time", that particular class was 2 hours long so I figured it would be save just to turn it off right? Well the next day when I got to class I turned it on (after having been left off all night) you would think I would probably have about 2 hours of in-use time left right? Nope! It said "less than 1 day idle, less than 1 hour in use" that means not much left, and it actually ended up being about 5 MINUTES of usage time (on lowest brightness, blah blah), (that was pretty unfortunate too since I keep all my notes on my tablet ) anyway I will say that these days I just leave my tablet on all the time, even if I don't plan on using it for days. Hope this helps.